1. Field
This invention relates, in general, to display driver integrated circuits, and more particularly, to a display driver integrated circuit having a graphic random access memory (GRAM). The invention also related generally to memory control methods for display driver integrated circuits with GRAMs.
2. Description
Display driver integrated circuits (DDIs) are used to supply image data to pixels of display devices. Such a DDI may include a graphic RAM (GRAM). In one application, a DDI is used to drive an active matrix display device, for example an active matrix liquid crystal display (LCD) device. Such a display device typically includes a plurality of pixel elements arranged in rows and columns, with each pixel element including a field effect transistor (FET) as a pixel switching element. The gates of the FETs are all connected to corresponding gate lines (row lines) for receiving row selection signals, and the sources of the FETs are all connected to corresponding source lines (column lines) for receiving image data.
FIG. 1 illustrates an arrangement of GRAM cells 110 and source drivers 120 in a DDI 100 for supplying image data to a display device, such as an active matrix display device as described above. DDI 100 includes one source driver 120 for each column line of the display device to be driven by DDI 100. For example, in many display devices, three adjacent column lines of the display device drive three corresponding columns of sub-pixels for displaying three different colors (e.g., red, green & blue) to form pixels displaying an entire spectrum of colors. Meanwhile, three source drivers 120 are provided for the three column lines, supplying image data for the three colored sub-pixels forming each pixel. Moreover, as illustrated in FIG. 1, each column of GRAM cells 110 stores image data for three columns of sub-pixels in the display device. That is, each column of GRAM cells 110 provides image data to three source drivers 120—one for each of the three colors in a column of pixels.
As the degree of integration of the GRAM devices increases, the GRAM devices become smaller and smaller. However, in general, in today's technology a reduction in the width of GRAM cells 110 is not matched by a corresponding reduction in width of the source drivers 120. As a result, a column of GRAM cells 110 having a small width is disposed confronting three source drivers 120 whose combined width is greater than the width of the GRAM cells. In particular, under a 130 ns process, the size of the “face” of, e.g., three source drivers 120 is greater than the size of the corresponding “face” of GRAM cells 110.
So, a hardware design must consider how to interface the lines from GRAM cells 110 with the reduced width, to source drivers 120 having a greater width. This makes signal routing quite difficult, and leads to an increase in the area required for signal routing, as can be understood from FIG. 1. This is undesirable from the standpoint of the constant desire to reduce the overall size of DDI 100. Furthermore, there is a desire among the customers for DDIs for reduced chip height.
Accordingly, it would be advantageous to provide a DDI which can accommodate a reduction in the size of GRAM cells without an increase in the area required for signal routing. It would also be advantageous to provide a method of providing image data to source drivers for a display device which can operate without a large and difficult signal routing layout.
In one aspect of the invention, a method provides image data to source drivers for a display device comprising b*y rows and a*x columns of pixels, where b>a. The method comprises: receiving image data for b*y rows of pixels of the display device, the image data for each of the b*y rows of pixels including image data for each of the a*x columns of pixels of the display device; storing the image data for the b*y rows of pixels of the display device into a*y rows of memory cells in a graphics memory device, wherein each of the a*y rows of memory cells in the graphic memory device stores image data for an entire one of the b*y rows of pixels of the display device, and further stores image data for x columns of each of (b−a) other rows of pixels of the display device; and sequentially supplying the image data for each of the b*y rows of pixels of the display device from the graphic memory device to the source drivers.
In another aspect of the invention, a graphics memory device is adapted to provide image data to source drivers for a display device comprising b*y rows and a*x columns of pixels, where b>a. The device comprises: a memory array having a*y rows and b*x columns of memory cells, the memory array being adapted to store image data for b*y rows of pixels of the display device into the a*y rows of memory cells of the memory array, the image data for each of the b*y rows of pixels of the display device including image data for each of the a*x columns of pixels, wherein each of the a*y rows of memory cells of the memory array is adapted to store image data for an entire one of the b*y rows of pixels of the display device, and to store image data for x columns of each of (b−a) other of the b*y rows of pixels of the display device; and a memory location remapping circuit adapted to supply the image data for each of the b*y rows of pixels of the display device from the memory array to the source drivers.
In a further aspect of the invention, a graphics memory device comprises: a memory array configured to store data for a display device comprising b*y rows and a*x columns of pixels, where b>a, the memory array being arranged in a*y rows and b*x columns of memory locations, each memory location being adapted to store n-bit image data for one of the pixels of the display device; and a memory location remapping circuit adapted to remap image data stored in the b*x columns of memory locations in the memory array to the a*x columns of the display device.
In yet another aspect of the invention, a method of providing image data to source drivers of a display device comprising b*y rows and a*x columns of pixels, where b>a, comprises: storing n-bit image data for the pixels of the display device in a memory array arranged in a*y rows and b*x columns of memory locations, each memory location being adapted to store n-bit image data for one of the pixels; and remapping the image data stored in the b*x columns of memory locations in the memory device to the a*x columns of the display device.
In still another aspect of the invention, a method of providing image data to source drivers of a display device, comprises: receiving image data for blocks of b rows by a columns of pixels of a display device, where the image data is mapped to a rows by b columns; storing the mapped image data in blocks of a rows by b columns of memory locations in a memory array; and remapping the image data stored in the blocks of a rows by b columns of memory locations in a memory array, to the b rows by a columns of pixels of a display device, where b>a.
In a still further aspect of the invention, a graphics memory device comprises: a memory array configured to store image data for blocks of b rows by a columns of pixels of a display device in blocks of a rows by b columns of memory locations; and a memory location remapping circuit configured to remap the image data stored in the blocks of a rows by b columns of memory locations in a memory array, to the b rows by a columns of pixels of a display device, where b>a.